Opening method for poultry carcasses

ABSTRACT

A bird is gripped by its thighs adjacent the vent hole and is shifted toward a knife until the hole has reached a predetermined location that corresponds to a certain depth of insertion of the knife into the hole. Since location of the hole is being used as the determining factor with respect to depth of knife insertion, the knife always enters to the same extent regardless of the length of the bird. Operation of the knife once fully inserted causes the skin to be slit between the hole and the keel bone, thus making an enlarged opening to the body cavity.

TECHNICAL FIELD

This invention relates to the preparation of poultry carcasses for humanconsumption and, more particularly, relates to that stage of the processfollowing the initial cut around the vent of a bird for the purpose ofremoving the latter and leaving an entry hole to the body cavity.

BACKGROUND ART

It is desirable to make the dimensions of the initial cut around thevent of the bird as small as possible so that the "plug" of materialremoved contains only a minimal amount of edible meat. On the otherhand, it is necessary to thereafter enlarge this entryway into thecavity because its dimensions are too small to permit the entry of atool for removing the viscera within the cavity. Consequently, it haslong been the practice to manually slit the skin between the vent holeand the keel bone of the bird so as to provide an opening of therequisite dimensions without sacrificing edible portions of the bird.

Various efforts have been made to automate this enlarging or "opening"step, but none has heretofore been entirely successful for a number ofreasons. Included among these is the fact that many prior openingmechanisms have simply been unduly complicated. Additionally, many havebeen unable to satisfactorily make the opening cut without alsopuncturing or otherwise unintentionally damaging the organs disposedclosely beneath the skin intended to be severed. The latter type ofmishap results in spewing contaminated fluids over the otherwise edibleportions of the bird to the end that the entire bird may be unfit forconsumption. Examples of method and apparatus to overcome these priorshortcomings are diclosed and claimed in prior copending application,titled "Method and Apparatus for Opening the Body Cavity of Poultry,"Ser. No. 835,671, filed Sept. 22, 1977, in the names of Scheier, et al,and assigned to the assignee of the present invention.

While the arrangement described and claimed in the aforesaid applicationhas indeed proven to be a significant improvement over prior openingmethods and machines, it has been found that by limiting the extent towhich the slitting knife can move in a certain direction correspondingto its depth of insertion into the hole of the bird, the actual depth ofinsertion can vary depending upon the particular length of the birdbeing processed. In other words, the knife in the aforesaid applicationis not adjustable relative to the length of each bird it encounters, andinstead comes to a certain fixed position each and every operation,regardless of whether the bird is long or short. Hence, it is possiblethat the knife might be inserted more deeply into short birds than longones, since both are suspended by their hocks from an overhead conveyor.Excessive depth of penetration of the knife could result in accidentalpuncture of the intestines and other organs containing contaminants thatwould spoil the meat.

It is known in the art to associate the slitting knife with a speciallocating carriage that does not permit operation of the knife until suchtime as the carriage has reached and engaged the stern of the bird,whatever its length. Once the stern has been engaged, the knife can movethrough its predetermined slitting movements with the assurance that thesame depth of penetration will be achieved regardless of the length ofthe bird.

SUMMARY OF THE INVENTION

Such prior devices wherein the knife is adjusted according to thelocation of the stern of the bird are unsatisfactory for a number ofreasons, not the least of which is complexity. Accordingly, a feature ofthe present invention is to provide a more simplified, yet highlyreliable, arrangement which accommodates variations in bird lengths bybringing the sterns of all birds to the same fixed location that isstrategically situated with respect to the knife. In other words,instead of adjusting the knife for each bird size, compensation is madeby the birds while the knife position never changes in this regard. Inthis manner, regardless of whether the particular bird being processedis long or short, its vent hole is placed at precisely the same positionwith respect to the knife as those birds which have preceded theparticular one being slit and those which will follow.

In many respects, the present invention is an extension of and animprovement upon the teachings of the aforesaid application to theassignee of this invention, and yet, in other important respects, thepresent invention is not limited to the specific features of saidearlier application. In this regard, while the motion of the kniferemains the same, the motion of the bird is different. In the presentinvention, the bird is grasped by its thighs adjacent the vent hole andis bodily moved toward the knife until the hole reaches a predeterminedposition. Although the distance through which the bird is shifted isconstant for all birds, because they are all engaged adjacent theirholes by the structure which effects their shifting, the overall lengthsof the various birds is never a factor. In other words, if the birdswere pulled toward the knife by their hocks for a fixed distance, thenwhether the legs were long or short would make a difference with respectto the final location of the holes. But since the area which must beproperly located, i.e., the hole in the stern of the bird, is the samearea being used by positioning structure to shift and locate the bird,variations in leg lengths are of no consequence. Much the same is trueif the shoulders of the bird instead of the hocks were used to engagethe positioning structure. In that event, body length would be a factorin determining where the holes would ultimately be located.

In carrying out the principles of the present invention, each bird to beprocessed is suspended by an overhead conveyor with the hocks of thebird captured within a suitable shackle. As the bird advances along aprescribed course of travel, it is gently swung into the station of arotating, carrousel-type machine with its breast facing outwardly. Aspecially shielded knife, with its cutting edge trailing, swingsdownwardly and inwardly with respect to the rotating carrousel machine,and during such movement, the knife partially enters the previouslyformed hole at the vent of the bird. By the time such entry has beeninitiated, an upwardly swingable device is cammed into engagement withthe outside of the thighs of the bird, and as the device continues toswing upwardly, it lifts the bird up against a pair of spaced shoulderrods centered between the legs and against the stern of the bird. Thedevice essentially relieves the weight of the bird from the overheadconveyor at this time, and thus determines where the hole will belocated, rather than the conveyor. Consequently, the knife cannot beover-inserted to damage the entrails.

While the thighs of the bird are thus clamped by the device against thelocating shoulders, the knife flips outwardly to slit the skin betweenthe hole and the keel bone, whereupon the device drops away and returnsthe load of the bird to the overhead conveyor.

BRIEF SUMMARY OF THE DRAWINGS In the drawings

FIG. 1 is a fragmentary elevational view, partially in cross section, ofapparatus constructed in accordance with the principles of the presentinvention and capable of carrying out our novel method;

FIG. 2 is a cross-sectional view through the apparatus taken along line2--2 of FIG. 1;

FIG. 3 is a front elevational view of one of the several slitting unitsof the apparatus;

FIG. 4 is an enlarged, fragmentary elevational view of a knife of one ofthe units, the protective casing for the knife being partially brokenaway to reveal details of construction;

FIG. 5 is an enlarged, fragmentary front elevational view thereof;

FIG. 6 is a fragmentary, top plan view of the cam track for thebird-positioning devices of the units and illustrating one of suchdevices in a position approaching the track;

FIGS. 7, 8 and 9 are schematic side elevational views of one of theslitting units illustrating successive steps in operation of the knifeand the bird-positioning device;

FIG. 10 is a front elevational view of the unit corresponding to thecondition of things in FIG. 9;

FIG. 11 is an enlarged, fragmentary, side elevational view of the knifein a position corresponding to that of FIGS. 9 and 10 with the bodycavity of the bird illustrated in cross section; and

FIG. 12 is a side elevational view comparable to FIGS. 7, 8 and 9, butshowing the position of the knife and the shifting device immediatelyfollowing the slitting stroke.

DETAILED DESCRIPTION

As illustrated primarily in FIGS. 1 and 2, the apparatus includes aframe 10 consisting of, among other things, uprights 12 and 14,vertically extending angle members 16 and 18, and various horizontalbraces such as 20, 22, 24 and 26, that rigidify the frame 10. In theillustrated arrangement, uprights 12 and 14 are ground-engaging whileangle members 16 and 18 are not, thereby requiring that members 16 and18 be secured to some overhead support or the like so as to stabilizethe frame 10. The particular design of the frame 10, of course, haslittle direct bearing on the principles of the present invention.

A central upright stationary structural pipe 30 extends the full heightof the frame 10 and is surrounded adjacent its upper end by a sleeve 31that may be rotated within a bearing 32 which remains stationary withpipe 30. Sleeve 31 is then affixed to an impulse wheel 34 so that thewheel 34 and the sleeve 31 may rotate together about the uprightlongitudinal axis of the pipe 30. The wheel 34 is provided with a numberof circumferentially spaced retaining devices 36 at its outer peripherybetween which are received depending trolleys 38 of a bird conveyor 40.The trolleys 38 ride along an overhead track 42 and are powered by meansnot illustrated so that advancement of the conveyor 40 transmits drivingpower to the wheel 34 through the retaining devices 36 to rotate thewheel 34 at the same peripheral speed as the lineal speed of theconveyor 40. The track 42 of the conveyor 40 encircles the machinethrough approximately 270 degrees thereof.

Each of the trolleys 38 carries a suspended link 44 which in turnswingably supports a shackle 46. The particular construction of shackle46 is well-known to those skilled in the art and will not be describedfurther herein. Suffice it to point out that a bird is suspended fromthe shackle 46 by its hocks in the manner illustrated, for example, inFIGS. 7, 10 and 12. A guide bar 48, disposed in a horizontal plane andlooped around the machine in a generally U-shaped configuration asillustrated in FIG. 2, is formed to have various portions thereofdisposed at certain selected radial distances from the axis of pipe 30so as to engage the inner sides of the shackles 46 during theiradvancement and displace the same radially inwardly or outwardly as thecase may be.

Substantially midway down the central axis of the apparatus, there is aplate 56 that is secured to a second lower sleeve 58 which surrounds thepipe 30 in the same manner as the upper sleeve 31. The lower sleeve 58is supported for rotation by a lower bearing 59 that is stationary withthe pipe 30 in the same manner as the upper bearing 32, and the upperend of lower sleeve 58 is connected to the underside of wheel 34 byfastening means 61 to receive driving power therefrom and thereby causerotation of the plate 56 with the wheel 34. Twelve slitting units, eachbroadly denoted by the numeral 60, are circumferentially spaced aboutthe periphery of the plate 56 for rotation with the latter, the units 60being identical to one another in construction and operation.

Each of the units 60 includes a pair of upright posts 62 spaced apartslightly in a circumferential direction and rigidly affixed at theirlower ends to the plate 56. A pair of sleeves 64, which may be tiedtogether by a bridge 66, are slidably carried by respective ones of theposts 62 for rectilinear movement up and down the latter. One or morecoil springs 68 encircling the posts 62 between the sleeves 64 and astop 70 across the tops of the posts 62 yieldably bias the sleeves 64downwardly toward the plate 56.

The sleeves 64 of each unit 60 are pivotally attached at their lowerends to a common link 72 that extends downwardly through an aperture 74(FIG. 2) in the plate 56 for pivotal connection below the latter withone arm 76 of a bell crank 78. The other arm 80 of the bell crank 78carries a knife 82, and the bell crank 78 is pivotally supported forinward and outward swinging movement about a pivot 84 by a pair oflaterally spaced arms 86, depending diagonally from the plate 56 andrigidly affixed to the latter against movement relative thereto.

As illustrated in FIGS. 4 and 5, the knife 82 includes a blade 88 havinga rectilinear cutting edge 90. The blade 88 has a pair of locatingnotches 92 at its opposite ends which receive locating pins 94 so as toposition the cutting edge 90 diagonally across a notch 96 in theprotective casing 98 that houses the blade 88. For the sake ofconvenience, the casing 98 may be constructed in two halves, comprisingone half 100 that is fixed to the arm 80 and a second half 102 which maybe held against the first half 100 by screws 104, thereby releasablyclamping the blade 88 in place.

The arm 80 of bell crank 78 projects downwardly through a generallyhorizontally extending loop 106 which is rigidly attached at its innerend to a pair of depending struts 108. The struts 108 are spaced apartslightly in a circumferential direction with respect to the circularplate 56 so as to receive therebetween the arm 76 of the bell crank 78,and the struts 108 are rigidly secured to the plate 56 for rotation withthe latter. A bar 110 interconnects the struts 108 across their lowerends.

Each pair of sleeves 64 carries a radially inwardly disposed commonroller 114 that serves as a cam follower for a cam track 116 in thenature of a rod looped around the central axis of the apparatus. Whilethe track 116 is circular in plan as viewed in FIG. 2 and is disposedconcentrically with respect to the axis of pipe 30, it has portionsthereof that rise and fall so as to control the vertical position of thesleeves 64 and hence the in-and-out position of the knife 82 of eachunit 60. To this end, the track 116 includes a stretch 116a that,beginning at point A, rises gradually yet steadily for approximately 135degrees of the track 116 until point B is reached where it suddenlydrops down to a second stretch 116b which continues at the same levelthroughout the remaining 225 degrees. A spider 118 having a plurality ofsupporting legs 120 attaches the track 116 to a cylinder 122concentrically disposed about the axis of pipe 30, but immobile relativeto the latter by virtue of a connecting member 124 that joins thecylinder 122 with the frame 10.

At the lowermost ends of the struts 108, a pair of bars 126 (FIG. 6)project outwardly for a short distance above the bar 110 and inperpendicular relationship to the struts 108. The outermost ends of thebars 126 carry transverse pivots 128 by which a generally U-shapeddevice 130 is swingably attached to the struts 108 for up-and-downmovement. The device 130 includes a pair of rigid side arms 132 thatembrace the bars 126 outside of the latter and which extend a shortdistance rearwardly of the upright struts 108 where they areinterconnected by a bight member 136. The bight member 136 carries arearwardly extending cam follower roller 138 disposed for operatingengagement with a stationary cam track 140 situated below the bearings59, as illustrated in FIG. 1.

As shown perhaps most clearly in FIG. 6, the cam track 140, while beingdisposed about the central axis of the upright pipe 30, has portionsthereof that rise and fall and which are disposed at varying radialdistances from the axis of the pipe 30 so as to control the position ofthe device 130 during movement of the same with the remainder of theunit 60 during rotation about the axis of the pipe 30. In this regard,the track 140 has a portion 140a that, beginning at point X, slopesprogressively downwardly and outwardly until point Y, whereupon asubstantially level portion 140b takes over. The portion 140b extendsslightly radially inwardly over its full length until point Z isreached, at which location portion 140c turns abruptly inwardly andupwardly for the remainder of the track 140.

FIGS. 2 and 6 view the machine in substantially the same direction sothat various points along the two cam tracks 116 and 140 can be readilycompared. In this regard, point A of cam track 116 begins at least 45degrees before point X of cam track 140 when the tracks 116 and 140 aretraversed in a clockwise direction. Point B of the track 116 occurs veryslightly after point Y on the track 140. Thus, the upwardly inclinedportion 116a of the track 116 corresponds generally with the downwardlyand outwardly inclined portion 140a of the track 140, with the exceptionthat the portion 116a starts substantially earlier than the portion 140aand terminates slightly after the termination of the portion 140a.Portions 140b and 140c of the track 140 occur during the portion 116b ofthe track 116.

As illustrated perhaps best in FIGS. 1, 9 and 12, the follower roller138 is disposed for engagement with the underside of the track 140 so asto be depressed by the latter as the unit 60 moves around the axis ofthe pipe 30. A tension spring 142 yieldably biases the roller 138 intoposition for engaging the latter with the track 140 at the proper time,and also serves as a return means for the device 130 when the slittingoperation has been completed. A pair of ears 144 projecting laterallyoutwardly from opposite ones of the struts 108 adjacent their lowermostends serve as stops for the device 130 against the action of the spring142 and are in position to be engaged by the arms 132 of the device 130when the latter is swung by the spring 142 in a direction to raise theroller 138.

Each of the arms 132 has at its outer end beyond the corresponding pivot128 a specially formed rigid bird-engaging member 146, having a pair ofportions 148 and 150 that are essentially at right angles to oneanother, the portion 148 being perpendicular to its arm 132 and theportion 150 being substantially parallel to its arm 132. Moreover, theouter portion 150 is laterally offset from the inner portion 148 in sucha direction that the two outer portions 150 of the members 146 arecloser together than the two inner portions 148 thereof.

The loop 106 on the unit 60 carries locating shoulder means broadlydenoted by the numeral 152, such shoulder means 152 being disposedgenerally in opposition to the bird-engaging members 146 of the device130. To this end, the shoulder means 152 comprises a pair of elongated,rigid elements 154 generally below the loop 106 and having a section154a extending substantially parallel to superimposed portions of theloop 106 and a diagonally extending portion 154b which angles upwardlyuntil intersecting the loop 106 adjacent the outermost periphery of thelatter. As illustrated perhaps best in FIG. 3, each of the elements 154is slightly inboard of the corresponding overhead portion of the loop106, generally in vertical alignment with the corresponding outerportion 150 of the member 146 of the device 130.

Operation

The conveyor 40 moves in a clockwise direction about the apparatus 10 asFIG. 2 is viewed, and thus drives the interconnected wheel 34 and plate56 in the same clockwise direction through impingement of the trolleys38 against the retaining devices 36 of the impulse wheel 34. This alsoresults in the slitting units 60 being carried around the axis of pipe30 in registration with respective ones of the trolleys 38. Thus, as thesuspended birds approach the revolving mechanism in the direction of thearrow 156 in FIG. 2, they are successively intercepted by the units 60and processed thereby until being released on the opposite side of themechanism for travel in the direction illustrated by the arrow 158.

The unit 60 in position I of FIG. 2 (see also position I in FIG. 6) issubstantially in the condition illustrated in FIG. 7 at this point inits revolution. Note in that figure that the cam follower 114 is ridingalong the low stretch 116b of cam track 116 and that therefore the knife82 is disposed outwardly and upwardly to its furthest extent in whatmight be described as its operated position. The guide bar 48 has arelatively radially inwardly disposed stretch 48a at this location suchthat the shackle 46 is closer in to the axis of the upright pipe 30 thanwill be true in certain subsequent positions. The bird 160 is straddlingthe loop 106 at this time and, of course, the vent cut in the bird 160has already been made, leaving a dangling plug not shown and a hole 162which may be seen only in FIG. 11. Also at this time the follower 138 ofthe device 130 has not yet reached its cam track 140 (see FIG. 6) sothat the device 130 is fully up against the stops 144 and is yieldablymaintained in that position by the spring 142. The bird 160 has slippedbetween the members 146 of the device 130 and the elements 154 of thelocating shoulder means 152 are overlying the stern of the bird 160 onopposite sides of the hole 162.

As the bird 160 and unit 60 progress around to point II in FIG. 2 (seealso position II in FIG. 6) corresponding to the condition of things inFIG. 8, the follower 114 encounters the stretch 116a of track 116 andthus begins to raise the sleeves 64, hence swinging the knife 82downwardly and inwardly about the pivot 84 by virtue of operating link72 and bell crank 78. Note that during this motion the "backside" of theknife 82 leads with the cutting edge 90 trailing.

Also by this time, a second stretch 48b of guide bar 48 has beenencountered by the shackle 46, such second stretch 48b being disposedradially outwardly to a greater extent than stretch 48a, and thus havingthe tendency to slightly swing the bird 160 outwardly. As shown in FIG.6, the follower 138 of the device 130 has still not yet reached its camtrack 140 so that the device 130 remains unactuated against the stops144.

As the bird 160 and its slitting unit 60 travel around approximately toposition III of FIG. 2 (see also position III in FIG. 6) correspondingto the condition of things in FIG. 9, the stretch 116a of cam track 116raises the sleeves 64 to their fullest extent so as to swing the knife82 downwardly and rearwardly to a position which may be termed its"cocked position." Thus, the swinging stroke of the knife 82 between theextreme positions of FIGS. 7 and 9 could be referred to as the cockingstroke for the knife 82.

At the same time that the knife 82 is swung downwardly and inwardly withthe cutting edge 90 continuing to trail, the bird 160 is likewise swunginwardly by virtue of the fact that a third stretch 48c of the bar 48permits this type of movement on the part of the bird 160. As the knife82 thus backs along its path of swinging travel, the bird 160 islikewise swung inwardly toward the struts 108 in such a way that thehole 162 intersects and receives the knife 82.

During the rotation of the apparatus from position II to position III,the follower 138 of the device 130 will have engaged the track stretch140a of cam track 140, causing the device 130 to swing in a clockwisedirection viewing FIG. 9 against the bias of the spring 142, henceforcing the members 146 into engagement with the outside of the thighsof the bird 160 closely adjacent the stern and at the same level as thehole 162. Continued clockwise movement of the device 130 causes themembers 146 to apply a lifting force against the thighs to such anextent that the bird 160 is actually raised up until such time as thelocating shoulder elements 154 engage the stern on opposite sides of thehole 162. The thighs actually become clamped in place between themembers 146 and the elements 152 to such an extent that the weight ofthe bird 160 is substantially relieved from the shackle 46.

Note as shown in FIG. 10 that because of the special formed nature ofeach member 146, while the inner portions 148 of the members 146 engagethe bird 160 along the backside of the outer surface of the thighs, theouter portions 150 of the members 146 are curled around in front of thethighs to such an extent that movement of the bird 160 radiallyoutwardly of the machine is effectively precluded. The clamping actionis thus so complete that the area of the bird 160 adjacent its hole 162is effectively immobilized in all directions. The limit of upward travelof the bird 160 is determined by the cam track 140 and, moreparticularly, by point Y. Thus, the distance through which the bird 160rises toward the knife 82 is fixed, regardless of the length of the birdor the diameter of its thighs.

As a result of this special positioning of the bird 160, insertion ofthe knife 82 into the hole 162 is finalized to the extent illustrated inFIGS. 9, 10 and 11. In other words, while the knife 82 can swing nofarther downwardly than the cocked position of FIG. 9 as a result of thelength of the arm 80 and the location of the pivot 84, the final depthof insertion of the knife 82 is not determined until the bird 160 hasbeen lifted and clamped upwardly against the locating elements 154. Byhaving the lifting device 130 engage the bird 160 at the same level asits hole 162 and by using this point of engagement as the place wherethe lifting force is applied for a fixed distance, this assures that thehole 162 will ultimately be in the same position with respect to theknife 82 as all prior birds and all subsequent birds, regardless of bodyand leg length. Hence, the danger of over-inserting to a depth whichwould cause the knife 82 to sever the entrails and release theircontaminating contents is avoided.

In position III the cutting edge 90 is inclined forwardly with respectto the path of swinging movement 164 (FIG. 11) of the blade 88, and isthus perfectly positioned to begin the slitting stroke through the skin166 between the hole 162 and the keel bone area 168. Consequently, bythe time the bird 160 and its slitting unit 60 have advanced to positionIV of FIG. 2 (see also position IV of FIG. 6), the cam follower 114 willhave passed point B on track 116 and fallen off the stretch 116a ontothe lower stretch 116b, allowing the spring 68 to quickly flip the knife82 outwardly and upwardly along the path 164 to slit the skin 166. Thisswinging stroke on the part of the knife 82 may be conveniently referredto as the slitting stroke; and, as is apparent, it is carried out muchmore rapidly than the cocking stroke during which the follower 118gradually rides up the sloping cam stretch 116a. As seen in FIG. 12, theknife 82 has returned to its operated position, and yet, during itsquick movement to such position, the device 130 has maintained the legsof the bird 160 clamped tightly against the locating elements 154 sincethe cam track portion 140b between points Y and Z is essentially thesame radial distance from the central axis of the pipe 30 all along thelength of the portion 140b. Noteworthy is the fact that the point B oncam track 116 controlling knife movement is slightly beyond point Y onthe track 140 controlling movement of the device 130. Thus, the slittingstroke of the knife 82 is not begun until the device 130 has reached theupper limit of its clamping movement against the thighs of the bird 160.

Beyond position IV, the cam track 140 allows the spring 142 to returnthe device 130 to its normal unactuated position against the stops 144,thereby freeing the bird 160 for removal from the apparatus. Note thatas the device 130 is returned to its position against stops 144, theweight of the bird 160 is returned to the shackle 46. Inasmuch as theconveyor 40 departs from the apparatus as the device 130 releases thebird 160, the bird 160 is swung away from its unit 60 for furtherprocessing as may be necessary or desirable.

Note that as the knife 82 backs along path 164 during its cockingstroke, the cutting edge 90 is not exposed to the skin 166 because thebackside of the case 98 leads. Moreover, as the hole 162 intersects andreceives the knife 82, it is the rounded lowermost tip of case 98 thatenters the hole 162. Thus, the tip is in position to push any organsthat it may encounter downwardly and away from the skin 166 and thecutting edge 90 and, in any event, is in position to maintain thecutting edge 90 at a distance from such organs during the ensuingslitting stroke along path 164. Consequently, the risk of puncturing orsevering the organs so as to release contaminated fluids is minimized.

We claim:
 1. In a method of making an enlarged opening to the bodycavity of a bird by inserting a knife into a hole at the stern of thebird and then using the knife to slit the skin between the hole and thekeel bone of the bird, the improvement comprising:clamping only thethighs and legs of the bird against stationary shoulder means at a knownrelationship to the knife before inserting the latter into the hole ofthe bird while leaving the remaining trunk portion of the bird otherwiseunrestrained; and continuing to maintain the bird clamped only by itsthighs and legs throughout the inserting and slitting steps so that thehole of the bird will remain properly positioned during the insertion ofthe knife, yet the trunk portion of the bird may yield outwardly duringthe slitting stroke of the knife to thereby avoid damage to the keelbone and excessive slitting of the skin.
 2. In a method as claimed inclaim 1, wherein the bird is shifted by its thighs to said shouldermeans for clamping.
 3. In a method as claimed in claim 1, wherein thebird is suspended from overhead means prior to said clamping; andlifting the weight of the bird off said overhead means during saidclamping.
 4. In a method as claimed in claim 3, and the additional stepof conveying the bird along a prescribed course of travel using saidoverhead means prior to and after said clamping.
 5. In a method asclaimed in claim 1, and the additional step of conveying the bird alonga prescribed course of travel throughout the process of making theenlarged opening.